Radio broadcast selecting and distributing system



Jan. 6, 1925. 1,522,360

E. E. CLEMENT RADIO BROADCAST slansc'rme AND Drs'rmu'rms sls'ml Filed Feb. 29. 1924 ill' Patented Jan. 6, 1925.

EDWARD E. CLEMENT, 0F WASHINGTON, DISTRICT OF COLUMBIA. ASSIGNOR TO ED- PATENT OF WARD F. COLLADAY. OF TVASHINGTON, DISTRICT 0F COLUMBIA.

RADIO BROADCAST SELECTING AND DISTRIBUTING SYSTEM.

Application filed February 29, 1924.

To all Lc/wm it may concer-n:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing at llf'asliingtoli, in the District of Columbia, have invented certain new and useful Improvements in Radio Broadcast Selecting and Distributing Systems, of which the following is a specification, reference being had therein to the accompanying drawing.

My invention relates to systems for radio broadcast distribution and has for its object to render it possible for subscribers with a very simple type of receiving apparatus to be able to select with certaintyv and receive with ample power from any distant station within the range of the present high powered long range receivers, such as the superheterodyne. Other objects will suiliciently appear hereinafter.

I attain my object by providing each subscriber to the system with a receiving antenna and tuned secondary circuit as usual, and I supply each subscriber from a. central station with unmodulated pulsating current at a frequency suitable to heterodyne with the carrier current received from any particular or desired distant station. In order to be able to do this, I install at a central station a plurality of oscillators tuned to different frequencies, and I provide the output terminals of these oscillator circuits with proper switching terminals, such as jacks or the like, so that they can be interconnected with the subscriber-s wired lines. In the connecting circuits, which may be ordinary cord circuits with terminal plugs, provided at the central oirice for connecting oscillators to the subscribers lines, I provide detector tubes, which rectify the oscillator currents, and since their plate circuits are connected to the lines, they supply the latter with unmodulated pulsating high frequency heterodyning currents. These currents are taken in at the subscribers station in one side of either a .differential circuit or in a differential receiver and therein combined with the modulated radio currents received over the antenna circuit, to produce locally an amplified modulated asymmetric beat wave, which is capable of being received on an ordinary radio telephone receiver, with or without the usual bridging phone condenser. Various types of local heterodyning circuit or instrument may be employed, the invention residing Serial No. 695,993.

particularly in the supply and transmission from the central station of unmodulated oscillator current at different frequencies, to enable the subscriber to make selection by heterodyning without the trouble of elaborate apparatus or tuning at his substation. An ancillary but very important feature of the invention is the furnishing of unmodulated pulsating ciurent for heterodyning whereby the beat'wave will be an asymmetric modiilatd wave, capable of being received in an ordinary radio telephone receiver, when properly connected, without further detection, thus obviating the necessity for detectors at the subscribers stations. Furthermore, the type of current thus supplied in the line circuits is suitable for communication back and forth between the subscribers and the opera-tors.

My invention is illustrated in the accompanying drawings in which- Fig. 1 is a diagram showing a central station and a subscribers station and connecting circuits for the same, together with oscillators at the central station.

Figs. 2 and 3 show subscribers receivers.

Referring to the drawing, Fig. 1, C is a central station and S is a subscribers station. At the former I locate oscillators O, O', O2, etc., having their circuits connected to switching terminals J, J J2, etc., whereby they may be interconnected with the switching terminals J3 of subscribers lines. The switching terminals in the drawings are shown as jacks, and the connecting means as plug cord circuits A and B. The cord A has a plug P and a plug P connected by conductors 1, 2, 3, 4, 1 and 3 constituting the input or grid circuit of a tube conductor D, the plate or output circuit of which is connected through the plug P to line wires 5 6 leading to the subscribers station.

The service rendered by the central station C to its subscribers includes a certain range in point of distance, and also a certain range in point of wave lengths throu h which selections can be made under t e supervision of the operators. For example, from 200 to 600 meters is the usual range of short wave lengths used in ordinary telephone broadcasting. The wave lengths supplied by the oscillators O, O', O2 should be such that they will form a heterodyning scale with the broadcasting wave lengths of the stations listed and intended to be rec ordinary headphone purposes.

ceived by the subscriber. Each subscriber will have to do his own tuning as at present, so far as his antenna circuit and local receiving circuit is concerned. but this 1s simple when the instrument is calibrated and standardized, involving merel)7 the setting of the variable condensers or equivalent apparatus to readings talren from a table. Beyond this the subscriber has nothing to do except to ask central for the station wanted. I-Ie is thereupon supplied with unmodulated oscillator current of such a frequency that the difference between it and the frequenc of the waves used by the station wanted. wi l be the uniform beat frequency to which all the subscribers instruments are standardized.

The operator is provided in each cord circuit with a key K by means of which she can include her headset H in the plate cir-4 cuit and therefore in series with the line and,

the subscribers instrument. It is possible to make this a bridging,r arrangement by using;` a bridging battery in the plate circuit, with radio and audio choke coils in the battery bridge. The plate-filament branch of the tube, the subscribers circuit, and anytemporary connection of the operators set would then all be in parallel with the battery, and the subscriber and the operator can talk back and forth on the high frequency high potential pulsating plate current. The same is true of the series arrangement.

Referringr to Fig. 2 I have shown therein a type of Fessenden receiver adapted to respond to heterodyne or beat wave effects produced in the manner thus described. In Fig. 3, I show an equivalent arrangement of coils, in which a single wound radio telephone receiver may be employed. In either case, the energy conveyed over the wired circuit by the unmodulated oscillator current is imparted to the beat Wave carrier, and thereby to the audio modulations. so as to produce an amplification suiiicient for If further amplification be desired. battery current being supplied over the line circuit from the central oflice to the subscrlbers station, as -usual 1n modern telephone systeme, may be used in a local audio amplified circuit, with No references cited.

a tube detector, which however I do not claim herein, as the same forms part of the subject matter of a separate application.

I claim:

l. In a system of radio broadcast distribution, a central station and subscribers stations and wired line circuits interconnecting them, means at a subscribers station for receiving modulated radio frequency carrier waves, means atthe central station for supplying the subscribers station over said wired line with unmodulated periodic current at such a frequency as will heterodyne with the modulated wares received at the subscribers station, to produce arstandard modulated beat wave in the subscribers receiver.

2. In a system of radio broadcast distribution, a central station and subscribers stations and wired line circuits interconnecting them, means at the subscribers station for receiving ether waves, means at the central station for generating unmodulated periodic current, switching means for connecting said central ot`ce generators interchangeably with said subscribers wired line circuits, and audio receivers at the subscribers station responsive to modulations carried on the standard beat waves due to the composition of the modulated and the unmodulated waves received through the ether and through the line circuits respectively.

3. In a system of radio broadcast distribution` a central station and subscribers stations and wired line circuits interconnectingr them. an oscillator circuit at the central ofiice, switching terminals therefor, switching terminals for the line circuits. and intermediate connecting circuits with terminals adapted to operate interchangeably with said switching terminals, each connecting circuit including a detector whereby the oscillator current is rectified and transmitted over the subscribers line as a high frequency unmodulated high potential puleating current. adapted to combine with received radio carrier waves to produce an asymmetric modulated beat wave.

In testimony whereof I hereunto affix my signature.

EDWARD E. CLEMENT. 

